Abstract and Figures

Perennial grain cropping systems could address a number of contemporary agroecological problems, including soil degradation, NO3 leaching, and soil C loss. Since it is likely that these systems will be rotated with other agronomic crops, a better understanding of how rapidly perennial grain systems improve local ecosystem services is needed. We quantified soil moisture, lysimeter NO3 leaching, soil labile C accrual, and grain yields in the first 2 yr of a perennial grain crop under development [kernza wheatgrass, Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] relative to annual winter wheat (Triticum aestivum L.) under three management systems. Overall, differences between annual and perennial plants were much greater than differences observed due to management. In the second year, perennial kernza reduced soil moisture at lower depths and reduced total NO3 leaching (by 86% or more) relative to annual wheat, indicating that perennial roots actively used more available soil water and captured more applied fertilizer than annual roots. Carbon mineralization rates beneath kernza during the second year were increased 13% compared with annual wheat. First-year kernza grain yields were 4.5% of annual wheat, but second year yields increased to 33% of wheat with a harvest index of 0.10. Although current yields are modest, the realized ecosystem services associated with this developing crop are promising and are a compelling reason to continue breeding efforts for higher yields and for use as a multipurpose crop (e.g., grain, forage, and biofuel).
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Agronomy Journal Volume 105, Issue 3 2013 735
Agronomy, Soils & Environmental Quality
Soil and Water Quality Rapidly Responds to the Perennial Grain
Kernza Wheatgrass
Steve W. Culman,* Sieglinde S. Snapp, Mary Ollenburger, Bruno Basso, and Lee R. DeHaan
Published in Agron. J. 105:735–744 (2013)
doi:10.2134/agronj2012.0273
Copyright © 2013 by the American Society of Agronomy, 5585 Guilford
Road, Madison, WI 53711. All rights reserved. No part of this periodical may
be reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopying, recording, or any information storage
and retrieval system, without permission in writing from the publisher.
A
   current agronomic research is to make
annual grain crop production more sustainable, with
management strategies that supply adequate fertility to meet
crop demand while conserving soil and water quality. For
temperate humid environments, these management strategies
typically strive to minimize soil disturbance (e.g., no-till and
conservation tillage strategies), maximize plant cover on the
soil (e.g., cover crops and no-till), and manipulate fertilizer
strategies and sources to reduce nutrient losses to the environ-
ment (e.g., organic amendments and precision agriculture)
(Robertson, 1997; Raun and Johnson, 1999; Snapp et al., 2005,
2010; Grandy et al., 2006).
e management choices that growers make can have dra-
matic impacts on local ecosystem services. For example, N fertil-
izer type, rate, and application in relationship to crop demand
are important regulators of N cycling eciency and loss path-
ways; this has direct and indirect consequences for water and
soil quality (Robertson, 1997; Snapp et al., 2010; Syswerda et
al., 2012). Despite the realized environmental benets of some
conservation management strategies, grower adoption of these
strategies can be limited for a variety of socioeconomic and bio-
physical reasons (Snapp et al., 2005; Grandy et al., 2006).
Another approach that has received far less attention than
management strategies for improving ecosystem services is to
“perennialize” annual grain systems via breeding for new peren-
nial grain crops (Glover et al., 2010b). e perceived benets of
this approach are based on inferences from agronomic research
that has consistently shown herbaceous perennial systems, such
as forages or restored or native grasslands, outperforming annual
cropping systems with regard to soil conservation (Montgomery,
2007), primary production and C cycling eciencies (Buy-
anovsky et al., 1987; Jenkinson et al., 1994; Silvertown et al.,
1994; Glover et al., 2010a; Zeri et al., 2011), N cycling ecien-
cies (Jenkinson et al., 2004; Glover et al., 2010a; Syswerda et
al., 2012), maintenance of soil nutrient stocks and soil C pools
(Buyanovsky et al., 1987; Jenkinson et al., 2004; Mikhailova et
al., 2000; Culman et al., 2010; Bremer et al., 2011), and mainte-
nance of soil food webs (Ferris et al., 2001; Culman et al., 2010;
DuPont et al., 2010). ese benets have been documented in
established herbaceous perennial systems, but future perennial
grain systems will likely be rotated with other crops and will
have to be reestablished with each rotation. e length of time
newly planted perennial crops need to improve ecosystem ser-
vices is very important because there have been some reports of
decreased ecosystem services in establishing herbaceous perenni-
als (McLaughlin et al., 2002; Syswerda et al., 2012).
One promising perennial grain crop is intermediate wheat-
grass, a widely adapted, high-yielding, cool-season forage grass
that provides excellent feed for livestock in the Great Plains
ABSTRACT
Perennial grain cropping systems could address a number of contemporary agroecological problems, including soil degradation,
NO3 leaching, and soil C loss. Since it is likely that these systems will be rotated with other agronomic crops, a better understand-
ing of how rapidly perennial grain systems improve local ecosystem services is needed. We quantied soil moisture, lysimeter NO3
leaching, soil labile C accrual, and grain yields in the rst 2 yr of a perennial grain crop under development [kernza wheatgrass,
inopyrum intermedium (Host) Barkworth & D.R. Dewey] relative to annual winter wheat (Triticum aestivum L.) under three
management systems. Overall, d ierences between a nnual and perennia l plants were much greater than dierences observed due to
management. In the second year, perennial kernza reduced soil moisture at lower depths and reduced total NO3 leaching (by 86%
or more) relative to annual wheat, indicating that perennial roots actively used more available soil water and captured more applied
fertilizer than annual roots. Carbon mineralization rates beneath kernza during the second year were increased 13% compared
with annual wheat. First-year kernza grain yields were 4.5% of annual wheat, but second year yields increased to 33% of wheat with
a harvest index of 0.10. Although current yields are modest, the rea lized ecosystem ser vices associated with this developing crop are
promising and are a compelling reason to continue breeding eorts for higher yields and for use as a multipurpose crop (e.g., grain,
forage, and biofuel).
S.W. Culma n, Kellogg Biological Station, Michi gan State Univ., 3700 E Gul l
Lake Drive, Hickor y Corners, MI 4906 0; S.S. Snapp, Kellogg Biologica l
Station and Crop and Soil Sciences Dep., Michiga n State Univ., 3700 E
Gull Lake Drive , Hickory Corners, MI 49060; M. Ollenburger, Crop and
Soil Sciences Dep., Michigan State Univ., 3700 E Gu ll Lake Drive, H ickory
Corners, M I 49060; B. Ba sso, Kellogg Biolog ical Station and Dep. of
Geological Sciences, Mich igan State Univ., 3700 E Gul l Lake Drive, Hickory
Corners, M I 49060; and L .R. DeHaan, e Land Institute, 2 440 E Water
Well Road, Salina, KS 67401. Received 2 0 June 2012. *Corresponding author
(steve.culman@gmail.com).
Abbreviat ions: POXC, permanganate-oxidizable carbon .
736 Agronomy Journal Volume 105, Issue 3 2013
and Intermountain West regions (Ogle et al., 2003; Hendrick-
son et al., 2005; Karn et al., 2006). is grass was identied as
a good candidate for domestication as a perennial grain crop
based on agronomic properties (Wagoner, 1990b) and because
the seed it produces is a nutritious and highly palatable grain
(Becker et al., 1991, 1992). Intermediate wheatgrass has been
under selection for grain via bulk breeding and mass selection
over the past two decades, with initial eorts at the Rodale
Research Center in Kutztown, PA (Wagoner, 1990a; Wagoner,
1995) and more recently at the Land Institute in Salina, KS
(DeHaan et al., 2005; Cox et al., 2010). e Land Institute has
named this newly developed, experimental grain kernza.
e limited number of studies on perennial grain cropping
systems have mostly reported on grain yields and plant traits
(Piper, 1998; Weik et al., 2002; Murphy et al., 2010; González-
Paleo and Ravetta, 2011; Hayes et al., 2012; Jaikumar et al.,
2012). To date, there have been no studies that have directly
quantied the soil ecosystem services gained in a perennial
grain system. Given this lack of empirical eld data regard-
ing soil C and N dynamics with perennial grain systems, we
examined the perennial grain crop kernza wheatgrass relative
to annual winter wheat using three management systems.
We were particularly interested in the length of time before
improvements in soil ecosystem services were detected. e spe-
cic objectives of this study were to: (i) determine the relative
impacts of perenniality and management on short-term soil N
leaching, C accrual, and soil moisture in a small grain cropping
system; and (ii) determine the yield potential of a newly devel-
oped population of kernza relative to annual wheat across the
three management systems.
MATERIALS AND METHODS
Site Description, Experimental Design,
and Management
e study was conducted at the W.K. Kellogg Biological
Station in Hickory Corners, MI (42°24¢ N, 85°24¢ W, eleva-
tion 288 m). e mean annual precipitation is 890 mm and
mean annual temperature is 9.7°C. e soils at this site are
Kalamazoo series (ne-loamy, mixed, semiactive, mesic Typic
Hapludalfs) with measured soil properties at 0 to 20 cm as
follows: pH = 5.5, soil organic C = 8.4 g kg–1 soil, total soil
N = 0.9 g kg–1 soil, Bray P = 27.7 mg kg–1 soil, sand = 548 g
kg–1 soil, silt = 379 g kg–1 soil, and clay = 72 g kg–1 soil. More
detailed soil information was provided by Syswerda et al. (2011)
and more general site information can be found at http://lter.
kbs.msu.edu/about/site_description/index.php. Previously, the
site was in a conventionally managed corn (Zea mays L.)–soy-
bean [Glycine max (L.) Merr.]–wheat rotation.
In the fall of 2009, a split-plot design with four replications
was established, with management as the main treatment and
plant species as the nested plots. e management systems
were: (i) organic management (Organic), (ii) conventional man-
agement, with 90 kg N ha–1 (Mid-N), and (iii) conventional
management, with 120 kg N ha–1 (High-N). e primary
dierences among the management systems were the fertilizer
forms and rates applied and the weed management strategies
(herbicides applied only in conventionally managed plots).
Organic and Mid-N treatments received the same rate of N
(90 kg N ha–1) but in dierent forms (poultry manure vs. urea),
while the Mid-N and High-N treatments diered only in the N
application rate (90 vs. 135 kg N ha–1, respectively). e Mid-N
treatment represents the recommended practice in Michigan
(Vitosh et al., 1995), and the High-N treatment received 50%
more N than the Mid-N treatment. Within each main plot, two
plant species were planted: Caledonia annual wheat and peren-
nial intermediate wheatgrass (kernza). e kernza seed used was
from a breeding population derived from one cycle of selection
primarily for seed size and yield per spike (Cox et al., 2010).
e parents used to create the population had previously been
through one to two cycles of selection by the Rodale Institute
and the USDA Big Flats Plant Materials Center.
Before planting, the site was chisel plowed to 20 cm and
limed with 2240 kg ha–1 of dolomitic lime. Mid-N and High-
N plots received pelleted urea as a starter at 33.6 kg N ha–1
and K2O at 53.8 kg K ha–1. Soils at this site are naturally high
in available P, and soil tests recommended no P fertilization.
Organic plots received 2240 kg ha–1 of commercially available
pelletized poultry manure (a mix of layer poultry manure and
sawdust at 4–3–2 N–P–K from Herbruck’s Poultry Ranch,
Saranac, MI). is application rate supplied 90 kg ha–1 total N
equivalent. All fertilizer was surface applied and then incorpo-
rated with a soil nisher.
In the rst year, population densities were kept consistent
between the annual and perennial plots. is required a com-
promise of higher than recommended seeding rates for the
intermediate wheatgrass and lower than recommended seeding
rates for the annual wheat. A very rainy and cool fall delayed
the initial planting. On 12 Nov. 2009, the plots were planted
with a grain drill at a rate of 310 seeds m–2 (1.25 million seeds
acre–1) at 15-cm row spacing. Annual wheat stands were rela-
tively thin and poor yields resulted (see below). In the following
year, the annual wheat seeding rate was increased to 432 seeds
m–2 (1.75 million seeds acre–1). Plots measured 3.66 by 5.5 m.
Conventional plots were topdressed with urea at 28 and 50.4
kg N ha–1 for the Mid-N and High-N treatments, respectively,
on 23 Apr. and 26 May 2010. Conventionally managed plots
were sprayed for broadleaf weeds with a mixture of thifensul-
furon-methyl (methyl 3-[[[[(4-methoxy-6-methyl-1,3,5-triazin-
2-yl)amino]carbonyl]amino]sulfonyl]-2-thiophenecarboxylic
acid) and tribenuron-methyl (methyl 2-[[[[(4-methoxy-6-
methyl-1,3,5-triazin-2-yl)methylamino]carbonyl]amino]sul-
fonyl]benzoate) at 5.4 mL ha–1, and Organic plots were hand
weeded in 2010. Annual wheat was harvested on 9 July 2010
and kernza was harvested on 8 Sept. 2010. Yields were assessed
by randomly placing two 0.25-m2 quadrats in the plot and clip-
ping whole plants 10 cm above the soil surface. reshed grain
weight (free of hulls) was determined and the average grain
weight and aboveground plant biomass between the two quad-
rats sampled per plot were reported. Subsamples were taken
for moisture determination by oven drying at 70°C for 72 h.
Oven-dry weights of grain and biomass are reported.
In the fall of 2010, elds were fertilized at the same rates as
the previous year, with the exception that no lime was applied.
Fertilizers were incorporated into the annual wheat plots
with tillage but were not incorporated in the perennial kernza
plots. In the annual wheat plots, the soil was tilled with a small
tractor-pulled rototiller rather than the chisel plow used the
previous year to preserve the instrumentation installed in the
Agronomy Journal Volume 105, Issue 3 2013 737
plots (see below), and the seed bed was rmed with a culti-
packer. Second-year annual wheat was planted on 8 Oct. 2010
at a rate of 432 seeds m–2. Conventional plots were topdressed
with urea at the same rates as outlined above on 5 April and
10 May 2011. No weed control was necessary in 2011. Annual
wheat and kernza were harvested on 21 July and 1 Aug. 2011,
respectively, using the methods described above.
Soil Moisture and Lysimeter Sampling
Soil moisture and lysimeter NO3 concentrations were
determined every 2 wk throughout the growing season. Soil
moisture was determined at four separate depths for each plot
(0–20, 20–40, 40–70, and 70–100 cm) using a Trime T3 time
domain reectometer probe (IMKO). Before planting, 5.1-cm
polyvinyl chloride tubes were installed vertically in every plot.
e tubes extended 1 m into the soil prole and were capped
when not in use to prevent moisture from entering the tube.
Prenart super quartz (polytetrauoroethylene/quartz) soil
water samplers (Prenart Equipment) were installed in every
plot on 18 to 19 Mar. 2010. At the edge of each plot, a 3.2-cm-
diameter tunnel was made with a steel drive point rod mounted
on a Geoprobe 540MT hydraulic probe assembly (Geoprobe
Systems). e tunnel was made at a 45° angle and extended
under the plot to a depth of 135 cm. Soil water samplers were
installed with a silica our slurry to ensure a good soil–sam-
pler interface, and the tunnels were backlled with soil and
sand. Irrigation boxes were installed at the edge of the plot to
house lysimeter collection bottles. On the same weeks that
soil moisture was determined, each lysimeter was sampled by
applying 50 kPa of vacuum for 24 h. Soil water was collected in
500-mL media bottles and the volumes of water collected were
determined by weight. Samples were ltered through a 2.5-mm
cellulose lter (Whatman no. 42) and frozen until analysis.
Nitrate concentrations of each sample were determined colori-
metrically with a continuous-ow analyzer (OI Analytical)
with a detection limit of 0.02 mg N L–1 for NO3.
Modeling Nitrate Loss
Tota l NO3 leaching in each system was modeled by combin-
ing the lysimeter NO3 concentrations with modeled soil water
drainage rates calculated using the Systems Approach for Land
Use Sustainability (SALUS) model (Basso et al., 2006, 2010).
e SALUS model simulates crop growth and soil processes
under various management practices over multiple years. e
soil water balance component of SALUS is based on the “cas-
cading bucket” approach to soil water movement through the
soil used in the CERES models but includes a revised method
for calculating runo, inltration, and evaporation (Basso et
al., 2010). Four separate buckets were modeled, reecting the
four depth proles at which soil moisture was measured (see
above). Management in each system was simulated based on
actual eld operations. e methods followed those described
more fully by Syswerda et al. (2012) for experiments conducted
at a nearby site in southwestern Michigan.
Measured lysimeter NO3 concentrations were averaged for
each plant × management combination on each date, and daily
values were interpolated using the package zoo in R (Zeileis and
Grothendieck, 2005). ese concentrations were multiplied
by the daily drainage rates to evaluate the total N mass ux
from the soil. To avoid overextrapolation, daily values were
interpolated only from the rst date of measurement (15 Apr.
2010) to the last of measurement (24 Oct. 2011), representing
the vast majority of two growing seasons. Root mean square
errors (RMSEs) indicated close agreement of modeled soil
water results with measured values. e RMSEs over both years
by the respective depths, 0 to 20, 20 to 40, 40 to 70, and 70 to
100 cm, were as follows: High N, wheat (0.054, 0.048, 0.028,
0.023); Mid N, wheat (0.053, 0.043, 0.033, 0.029); Organic,
wheat (0.050, 0.038, 0.025, 0.029); High N, kernza (0.057,
0.049, 0.051, 0.035); Mid N, kernza (0.059, 0.047, 0.034,
0.030); and Organic, kernza (0.055, 0.051, 0.044, 0.037).
Soil Sampling and Analyses
Soils were sampled on 16 to 17 June 2011 to three depths,
0 to 10, 10 to 20, and 20 to 40 cm. Six-centimeter-diameter
cores were taken with a Geoprobe 540MT hydraulic probe at
three randomly selected locations in the plot. e three samples
from each depth were composited, sieved to 6 mm, and mixed
until homogeneous.
Carbon Mineralization
One-day C mineralization was determined on rewetted soils
following Franzluebbers et al. (2000) and Haney et al. (2001).
e amount of water need to bring soils to 50% water-lled
pore space was determined gravimetrically for each depth
before the incubations. Ten grams of air-dried soil was weighed
in duplicate into 100-mL beakers and placed inside a 237-mL
canning jar. Deionized water was added to the soil, the jars
were capped tightly, and a zero-time CO2 concentration was
determined immediately by sampling 0.5 mL of air from the
headspace and injecting into a Li-Cor LI-820 infrared gas ana-
lyzer. e jars were incubated at 25°C for 24 h and a 1-d CO2
concentration was determined. Carbon mineralization was
determined as the dierence between the zero-time and 1-d
CO2 concentrations.
Permanganate-Oxidizable Carbon
All permanganate-oxidizable C (POXC) analyses and cal-
culations were based on Weil et al. (2003) and are described
fully at http://lter.kbs.msu.edu/protocols/133. Briey, 20 mL
of 0.02 mol L–1 K MnO4 was added to a 50-mL centrifuge tube
containing 2.5 g of air-dried soil. e tubes were shaken for
exactly 2 min at 240 oscillations min–1, allowed to settle for
exactly 10 min, and 0.5 mL of the supernatant was transferred
into a second 50-mL centrifuge tube and mixed with 49.5 mL
of deionized water. Sample absorbance was read with a Spec-
traMax M5 using Somax Pro soware (Molecular Devices) at
550 nm .
Statistical Analyses
Analysis of variance (ANOVA) was performed on soil and
plant data with the PROC MIXED procedure in SAS version 9.
Sampling time, soil depth, management system, and plant species
were treated as xed eects and block as a random eect, with
signicant dierences determined at a = 0.05. For soil moisture
analysis, due to computing constraints, we modeled each depth
separately, with sampling date as a repeated measure. Lysimeter
concentration data were also modeled, with date as a repeated
738 Agronomy Journal Volume 105, Issue 3 2013
measure and both years modeled independently. Modeled results
of daily NO3 uxes were determined as a single mean value for
each plant × management combination, so no statistical analy-
ses were performed on these data. Carbon mineralization and
POXC were modeled, with depth as a repeated measure. Means
were compared with an adjusted Tukey’s pairwise means com-
parison procedure using PROC MIXED in SAS. A ll graphing
was performed with the package ggplot2 (Wickham, 2009) in R
(R Core Team, 2011).
RESULTS AND DISCUSSION
Weather and Plant Development
Precipitation and temperatures during the spring (March–
May) diered dramatically in 2010 and 2011 (Fig. 1). Cumula-
tive precipitation in the spring was average in 2010 but was 55%
greater than average in 2011. Conversely, the spring of 2010
was the warmest spring in the past 24 yr at the Kellogg Biologi-
cal Station, with 253 more growing degree days (GDD) than
in 2011 (Fig. 1). ese weather factors, coupled with manage-
ment, impacted plant growth and development. e rainy, cool
conditions in the fall of 2009 resulted in a very late planting
date and minimal vegetative growth before vernalization, as
only 138 GDD accumulated between planting and 1 January
(Table 1). In contrast, a relatively early fall planting date and
warm fall in 2010 resulted in 487 GDD for wheat accumulated
before 1 January. (Kernza was well established by the fall of
2010.) Because temperature is a good predictor of leaf appear-
ance and development of winter wheat (Baker et al., 1986) and
because increased temperatures can lead to large yield reduc-
tions in winter wheat due to faster phenological development
(Rosenzweig and Tubiello, 1996), dierences in yields between
the years were expected (see below). Dierences in development
due to plant species were also apparent; kernza anthesis in 2010
was 41 d later than the annual wheat, while kernza anthesis in
2011 was only 20 d aer annual wheat (Table 1).
Soil Moisture
Total soil moisture varied greatly over the 2 yr and was primarily
aected by soil depth, sampling date, plant type, and soil texture
(Table 2; Fig. 2). Soil moisture was most strongly inuenced by
soil texture at the 0-to-20-cm and 70-to-100-cm depths (larger F
statistics for sand, Table 2) and by the sampling date for the surface
depths (larger F statistics at the 0–20-cm depth, Table 2). e
inuence of plant type on soil moisture was greatest at the 0-to-
20-cm and 70-to-100-cm depths. In contrast, management had no
signicant eect on soil moisture (data not shown).
Kernza had consistently lower soil moisture values at the low-
est depth (70–100 cm) compared with annual wheat (Fig. 2).
is suggests greater rooting activity at this depth or less drain-
age from surface depths to this lower depth (or both; see below).
Within the 0-to-20-cm layer in 2010, kernza had drier soils than
beneath annual wheat, but this trend was oen reversed in 2011.
e reason for this is not certain, but drier surface soil beneath
annual wheat could have resulted from greater evaporative losses
due to a less developed canopy or from increased rooting activity
Fig. 1. Cumulative growing degree days and precipitation from
March through July for the 2010 and 2011 growing seasons and
24-yr average at the Kellogg Biological Station, Hickory Cor-
ners, MI. Growing degree days were calculated by the method
of Baskerville and Emin (1969) with base = 0°C.
Table 1. Anthesis of annual wheat and perennial kernza wheat-
grass as affected by time and growing degree days at the
Kellogg Biological Station, Hickory Corners, MI.
Plant
Planting
date
Anthesis date
(d after planting)
Growing degree days
1 Jan. to
anthesis
Planting to
anthesis
———— °C d ———
2010
Annual 11 Nov. 2009 1 June 2010 (201) 1095 1233
Perennial 11 Nov. 2009 11 July 2010 (241) 1946 2084
2011
Annual 8 Oct. 2010 4 June 2011 (238) 921 1408
Perennial NA† 23 June 2011 (NA) 1317 NA
NA, not applicable; kernz a wheatgrass was not planted in 2011 because it was a
perennial second-year plant.
Table 2. Soil moisture F statistics and signicance by depth
generated from ANOVA with repeated measures analysis
by sampling date at the Kellogg Biological Station, Hickory
Corner s, MI.†
Year
Source of
variation
F-statistic
0–20
cm
20–40
cm
40–70
cm
70–100
cm
2010 S and content
(covariate)
39.1*** 130.8*** 60.4*** 201.1***
Plant species (P) 127.3*** 39.4*** 30.4*** 97.1***
Sampling date (D) 36.1*** 8.4*** 4.3*** 4.5***
D ´ P 4.5*** 1.8* 1.1 0.3
2011 S and content
(covariate)
52.3*** 106.4*** 44.1*** 215.4***
Plant species (P) 19.7*** 9.0*** 0.2 61.5***
Sampling date (D) 203.3*** 17.6*** 4.4*** 2.9***
D ´ P 6.8*** 1.3 1.0 0.3
* Signicant at P < 0.05.
*** Signicant at P < 0.001.
Management main ef fect s and interac tions were incl uded in t he mode l, but
yielded no signicant results (data not shown).
Agronomy Journal Volume 105, Issue 3 2013 739
and turnover in kernza that increased the soil pore space and
thus led to greater inltration during 2011.
Overall, there were dierences in soil moisture between
years, with the eects of plant type being stronger in 2010 than
2011 (F statistics in Table 2; pairwise comparisons in Fig. 2).
McIsaac et al. (2010) found similar trends regarding overall
lower soil moisture values during the establishment year of
annual row crops and perennial bioenergy crops relative to
subsequent years in Illinois. At our southwest Michigan site,
the 2011 growing season received ~150 mm more rain than
in 2010 (March–October), which likely alleviated some soil
moisture constraints and contributed to the limited dierences
observed with plant type in 2011 (Fig. 2).
Soil Nitrate Leaching
e concentration of lysimeter NO3 collected below the
rooting zone was not aected by plant species or management
in the establishment year (2010) but was strongly aected by
both factors in the second year (Table 3; Fig. 3). In 2010, lysim-
eter NO3 concentrations varied signicantly by date of sam-
pling but were not signicantly dierent due to management
or plant type. Lysimeter NO3 concentrations typically ranged
between 5 and 30 mg L–1 before harvest but started to show
trends regarding management and plant type in the second
half of the year (Fig. 3). Most notably, NO3 concentrations in
the High-N plots started to dierentiate by plant species, with
Fig. 2. Total volumetric soil moisture values for annual wheat (circles, dashed line) and perennial kernza wheatgrass (squares, solid
line) throughout four soil depths over the 2010 and 2011 growing seasons at the Kellogg Biological Station, Hickory Corners , MI.
Error bars represent one standard error of the mean. *Sampling time with signif icantly different (α = 0.05) soil moisture between
annual and perennial plants.
Table 3. Lysimeter concentration F statistics and signicance
generated from ANOVA with repeated measures analysis
by sampling date at the Kellogg Biological Station, Hickory
Corners, MI .
Source of variation
F-statistic
2010 2011
Management (M) 0.9 7.3**
Plant species (P) 0.1 32.9***
M ´ P 1.2 3.7†
Sampling date (D) 3.9*** 4.7***
D ´ M 1.5 0.9
D ´ P 1.6† 2.8***
D ´ M ´ P 1.4 0.6
** Signica nt at P < 0.01.
*** Signicant at P < 0.001.
† Signicant at P < 0.10.
740 Agronomy Journal Volume 105, Issue 3 2013
annual wheat plots showing upward trends in NO3 concentra-
tions. Management dierences also began to show in the latter
half of the season in annual wheat plots, where NO3 concentra-
tions under organic management trended downward relative to
the High-N plots (Fig. 3).
e 2011 season showed signicant dierences in lysimeter
NO3 concentrations due to plant type and management, with
the magnitude of the eect of plant type 4.5 times larger than
that of management (F statistic = 32.9 and 7.3, respectively;
Table 3; Fig. 3). e marginally signicant management ´
plant type interaction indicated that management had a larger
eect on NO3 levels in annual wheat than in kernza. e
High-N annual wheat plots showed greater lysimeter NO3
values (30–40 mg L–1) than the Mid-N and Organic plots
(10–20 mg L–1) during the growing season. Kernza plots did
not show the same pattern (P = 0.15). e Mid-N and Organic
kernza plots had virtually undetectable levels of lysimeter NO3
throughout the entire 2011 growing season, with only two
sampling points measuring >1 mg L–1.
Tota l NO3 leaching in each system was modeled by combin-
ing the lysimeter NO3 concentrations with modeled soil water
drainage rates in SALUS. Model results largely reect trends
in NO3 concentrations, showing minimal dierences in total
NO3 leached between annual wheat and perennial wheatgrass
in the rst year, while revealing large dierences in the second
year (Fig. 4; Table 4). Dierences in management in the rst
year appear to be more pronounced in the modeled NO3 leach-
ing data (Table 4) than in the NO3 concentration data (Table
3), indicating that drainage rates among the management treat-
ments had a substantial eect on the total NO3 lost.
Tota l N O3 lost in the second year of production (2011) was
driven primarily by plant type, although management also had
a large eect. Modeled results indicate that in the second year,
perennial kernza reduced total NO3 leaching by 85.8% in High-
N plots, 98.2% in Mid-N plots, and 99.4% in Organic plots rela-
tive to annual wheat during the growing season (Table 4). Man-
agement also had large eects on the total NO3 lost, as nearly
four times as much NO3 was lost from the High-N annual wheat
plots than the Organic annual wheat plots. e NO3 leaching
that we observed in annual wheat was within range of rates from
two long-term studies of a corn–soybean–wheat rotation: 62.3
to 70 kg NO3–N ha–1 yr–1 for a conventionally managed system
Fig. 3. Nitrate concentrations of soil water collected from lysimeters under annual wheat (circles, dashed line) and perennial
kernza wheatgrass (squares, solid line) plot s for three management systems over the 2010 and 2011 growing seasons at the Kellogg
Biological Station, Hickory Corners, MI. Error bars represent one standard error of the mean. *Sampling time with significantly
different (α = 0.05) lysimeter concentrations bet ween annual and perennial plants.
Agronomy Journal Volume 105, Issue 3 2013 741
and 19 to 40 kg NO3–N ha–1 yr–1 for reduced-input and organic
systems (Snapp et al., 2010; Syswerda et al., 2012).
Herbaceous perennial systems typically reduce subsurface
NO3 leaching compared with annual crops (Randall et al.,
1997; Mitchell et al., 2000; Huggins et al., 2001; Oquist et
al., 2007; McIsaac et al., 2010; Syswerda et al., 2012). Previous
studies have oen compared NO3 leaching rates of herbaceous
perennial systems that are not fertilized or not harvested (e.g.,
Conservation Reserve Program [CRP]) with annual crop-
ping systems. Our results add to the limited research on NO3
leaching in intensive annual and perennial cropping systems
that are both fertilized and harvested. In this study, we were
not able to dierentiate the relative eects of tillage vs. plant
species on N leaching rates in the second year, because the
annual wheat plots were tilled and perennial kernza plots
were not tilled in the fall of 2010. Regardless of this, no-till or
reduced-tillage management is an inherent feature of perennial
grain cropping systems, and so these eects will, by necessity,
co-occur and complement each other to reduce soil NO3–N
leaching.
Labile Soil Carbon
In this study, we did not measure soil organic C (SOC) levels
directly because these changes oen take years to detect (Wan-
der, 2004). Instead, we used two measures of labile organic
C as early indicators of SOC accrual or loss. One and a half
years aer the start of the experiment, C mineralization in the
kernza plots was signicantly greater than in annual wheat
(P = 0.026), but no dierences were detected for POXC (Table
5). In both measures of labile C, depth was signicant, while
management had no detectable eect.
Carbon mineralization rates reect the size of the biologi-
cally active organic matter pool because they typically corre-
spond well to long-term C mineralization rates, soil microbial
biomass, particulate organic matter, and N mineralization
potential (Franzluebbers et al., 2000; Haney et al., 2001).
Carbon mineralization has been shown to be a sensitive and
early predictor of total soil C sequestration in soils in both
perennial grasslands (Baer et al., 2002) and annual cropping
systems (Franzluebbers et al., 1994; Staben et al., 1997; Grandy
and Robertson, 2007). Aer 4 to 7 yr in CRP dominated by
wheatgrass species, Staben et al. (1997) found that C min-
eralization rates were signicantly greater under CRP than
Fig. 4. Cumulative total NO3– N leached under annual wheat
(dashed line) and perennial kernza wheatgrass (solid line)
plots for three management systems over the 2010 and 2011
growing seasons at the Kellogg Biological Station, Hickor y
Corners, MI . Values based on daily leaching fluxes from the
SALUS model.
Table 4. Cumulative NO3 losses for annual wheat and peren-
nial kernza wheatgrass under three management systems
during the growing seasons of 2010 and 2011 and over both
growing seasons at the Kellogg Biological Station, Hickor y
Corner s, MI.†
Plant
type
Manage-
ment
Cumulative NO3 leached
15 Apr.–
24 Oct. 2010
15 Apr.–
24 Oct. 2011
15 Apr. 2010–
24 Oct. 2011
— kg NO3–N ha–1 ———————
Annual High-N 24.3 69.8 148.3
Mid-N 9.8 27.5 53.8
Organic 11.3 17.7 45.1
Perennial High-N 17.7 9.9 32.0
Mid-N 12.7 0.5 15.0
Organic 11.6 0.1 15.3
To avoid overextr apol ation , daily ux values were interp olate d only fro m the
rst date of measurement (15 Apr. 2010) to the last dat e of measureme nt
(24 Oct. 2011).
Table 5. Soil permanganate-oxidizable C (POXC) and C min-
eralization by depth for annual wheat and perennial kernza
wheatgrass for the June 2011 sampling at the Kellogg Biological
Station, Hickory Corners, Michigan. F-statistics and signicance
from ANOVA are repor ted below the treatment means.
Depth Plant type POXC C mineralization
mg C g soil–1 mg CO2 g soil–1 d–1
0–10 cm annual 294 ± 13† 61 ± 3
perennial 308 ± 19 70 ± 2
10–20 cm annual 258 ± 16 48 ± 2
perennial 259 ± 12 49 ± 2
20–40 cm annual 114 ± 16 27 ± 2
perennial 118 ± 11 25 ± 2
F-statistic
Source of variation
M anagement
regime (M)
2.0 1.7
Plant species (P) 1.0 7.1*
M ´ P 1.2 1.7
Depth (D) 281.5*** 386.0***
D ´ M 0.2 1.7
D ´ P 0.4 7.2**
D ´ M ´ P 1.5 0.4
* Signicant at P < 0.05.
** Signica nt at P < 0.01.
*** Signicant at P < 0.001.
† Means ± s tand ard erro rs of the means .
742 Agronomy Journal Volume 105, Issue 3 2013
paired annual wheat sites. Permanganate-oxidizable C reects
a relatively processed pool of labile organic C and is a sensitive
indicator of ecosystem change (Weil et al., 2003; Culman et
al., 2012), but no dierences were apparent aer the rst 1.5
yr. Although these systems are undoubtedly still in ux, the C
mineralization results suggest that over a relatively short time,
more biologically active C is being stored in soils under kernza
than annual wheat.
Agronomic Yields
Annual wheat and perennial kernza diered substantially in
grain yield and vegetative biomass (Table 6). In 2010, annual
wheat yielded more grain and total aboveground biomass than
kernza. e following season showed higher grain yields for
both annual wheat and kernza, while aboveground vegetative
biomass remained similar for annual wheat but increased dra-
matically for kernza.
Annual wheat grain yields varied from 2.8 to 3.8 Mg ha–1 in
2010 and 4.2 to 5.0 Mg ha–1 in 2011 (Table 6) and were similar
to yields reported previously for wheat at this southwest Michi-
gan site (Smith et al., 2007; Snapp et al., 2010). e higher
yields in 2011 were likely due to multiple factors, including an
increase in seeding rate (see methods above), an earlier planting
date that allowed quicker stand establishment, and a decrease in
weed pressure in 2011. e weather in 2011 was also much more
amenable to small grain production, with a cooler and wetter
spring allowing ample vegetative growth before the beginning
of reproductive development. In 2010, increased weed pres-
sure due to higher available soil N was a likely reason for the
decreased annual wheat yields in the High-N and Mid-N plots
relative to the Organic plots; the trend was reversed in 2011 and
aligned more with what would typically be expected along a N
fertility gradient. In 2011, a high proportion of High-N kernza
plants lodged in a storm, leading to reduced aboveground bio-
mass relative to the Mid-N kernza plots.
Intermediate wheatgrass seed yields (including the seed
hulls) for established commercial forage cultivars are typi-
cally 168 to 280 kg ha–1 under dryland conditions and 504 to
616 kg ha–1 under irrigated conditions (Ogle et al., 2003; Weik
et al., 2002). Loeppky et al. (1999) reported a range of 269 to
442 kg ha–1 over a N fertilization gradient in northeastern
Saskatchewan; Lee et al. (2009) reported a range of 150 to
250 kg ha–1 over topographical positions in South Dakota.
Seed yields of forage cultivars as high as 800 to 950 kg ha–1
have been reported in the Great Plains (Wagoner, 1995). Our
second-year yields were higher than those previously reported,
ranging from 1390 to 1662 kg ha–1. is is likely due to a
number of factors. First, this is a new breeding population,
selected over the past 15 yr for seed size and yields, not for for-
age attributes. Second, seed yields in perennial grasses vary over
growing seasons, with yields typically peaking the second or
third year and then declining (Wagoner, 1990a). Most reports
of intermediate wheatgrass seed yields are from stands 3 yr or
older. Additional data will need to be collected to determine if
yields for this breeding population of kernza wheatgrass decline
over time. ird, most intermediate wheatgrass seed yields have
been reported from the Great Plains or Intermountain West,
under lower rainfall and fertility conditions than our site in
Michigan. Greater yields could be expected at our site, given
that both seed and vegetative productivity of intermediate
wheatgrass are responsive to inputs (Loeppky et al., 1999; Ogle
et al., 2003; Xue et al., 2011). Fourth, planting and tiller densi-
ties can vary considerably, as most intermediate wheatgrass
cultivars managed for forage seed are planted in rows at wide
spacing and these rows are maintained over the years. Our plots
were planted at 15-cm row spacing, but by the second year,
kernza rhizomes had created thick sod, greatly increasing the
tiller density relative to the rst year. Finally, most reports of
seed yields were from mechanically harvested plots. Our plots
were hand harvested and therefore likely overestimate realized
yields because a substantial amount of intermediate wheat-
grass seed can be lost during mechanical harvesting (Wagoner
1990 b).
e dierences in seed yield between annual wheat and
kernza were great (Table 6). Averaged across management
practices, rst-year kernza yielded 4.5% compared with annual
wheat in 2010, and second-year kernza yielded 33% compared
with wheat in 2011. e vegetative biomass of annual wheat
was 93% of the kernza biomass in 2010, whereas annual wheat
was only 29% of the kernza vegetative biomass in 2011. Seed
yield of kernza wheatgrass appears to be more sensitive to
late planting than winter wheat, perhaps due to the relatively
Table 6. Annual wheat and perennial kernza wheatgrass
grain and vegetative biomass yields and harvest index under
three management systems in 2010 and 2011 at the Kellogg
Biological Station, Hickory Corners, MI.
Year
Plant
type
Manage-
ment Grain yield
Vegetative
biomass
Harvest
index
— kg ha–1 ——————
2010 annual High-N 2807 ± 273 b† 3470 ± 367 0.45
Mid-N 2946 ± 266 ab 4021 ± 489 0.42
Organic 3761 ± 164 a 4416 ± 203 0.46
perennial High-N 157 ± 32 4984 ± 521 a 0.03
Mid-N 112 ± 15 3881 ± 376 b 0.03
Organic 156 ± 12 3982 ± 359 b 0.04
2011 annual High-N 5017 ± 340 4634 ± 210 0.52
Mid-N 4248 ± 425 4036 ± 338 0.51
Organic 4460 ± 628 3714 ± 607 0.55
perennial High-N 1428 ± 185 13083 ± 799 b 0.10
Mid-N 1662 ± 183 17131 ± 653 a 0.09
Organic 1390 ± 80 12202 ± 1004 b 0.10
F-statistic
Source of variation
2010
M anagement
regime (M)
4.4* 1.2 3.3‡
Plant species (P) 518.4*** 138.9*** 3271.6***
M ´ P 4.8* 13.5** 1.1
2011
M 0.5 4.4 2.8‡
P 159.6*** 166.7*** 2098.8***
M ´ P 1.4 11.2** 0.8
* Signicant at P < 0.05.
** Signica nt at P < 0.01.
*** Signicant at P < 0.001.
Means ± s tand ard erro rs. Me ans followed by different let ters i n the same
column represe nt signicantly different tre atmen t means within a plant s pecie s
and year.
‡ Signicant at P < 0.10.
Agronomy Journal Volume 105, Issue 3 2013 743
slower vegetative development of wheatgrass. Early planting of
kernza wheatgrass will oen result in earlier owering dates
and greater rst-year yields (DeHaan, unpublished data, 2012).
e late fall planting in 2009 and unusually warm spring likely
contributed to the lower seed yields and total aboveground bio-
mass production in 2010.
Intermediate wheatgrass is a very productive plant and
in recent biofuel evaluations, has performed comparably to
big bluestem (Andropogon gerardii Vitman) and switchgrass
(Panicum virgatum L.) in South Dakota (Lee et al., 2009) and
to switchgrass in North Dakota (Xue et al., 2011). In light of
the total aboveground productivity of kernza in the second
year, little of this xed C was allocated to seed (harvest index =
0.10). Total productivity is an important characteristic of
perennial grain crops because the greater allocation of photo-
synthate into reproductive eort has historically been a pri-
mary mechanism for increasing yields (Giord et al., 1984). If
the total aboveground productivity in the second year is main-
tained for several subsequent years and if continued breeding
eorts are able to increase the harvest index to ~0.30, kernza
would yield grain comparable to annual wheat. Past breeding
eorts with this grass have shown a large degree of genetic
diversity that can be manipulated, with 10 to 20% increases in
seed yield per selection cycle (Knowles, 1977; Wagoner, 1995;
Cox et al., 2002). It should be noted that any yield gains should
be balanced with ecosystem services.
Additional possibilities attainable in the near term would be
management of these systems as a multipurpose crop for forage,
grain, and biofuel. Previous work has explored the economic
possibility of an intermediate wheatgrass dual-use system (for-
age and grain; Watt, 1989), as well as a perennial wheat dual-use
system (Bell et al., 2008) because income from forage could o-
set the reduced income from lower yields in perennial systems.
CONCLUSIONS
is study examined soil moisture, soil C accrual, NO3
leaching, and agronomic performance of a new perennial
grain wheatgrass cultivar relative to annual wheat across three
management regimes. Overall, dierences between perennial
kernza and annual wheat impacted the measured soil proper-
ties much more than N management. In the rst 2 yr, kernza
demonstrated reduced NO3 leaching, lower soil moisture at
depth, increased labile soil C, but reduced yields of grain. Con-
tinued evaluations are needed to determine how these systems
perform over time, and continued breeding eorts are neces-
sary to increase grain yields. Kernza shows promise, however,
for rapidly improving local soil ecosystem services and for
addressing some of the most chronic environmental challenges
associated with current food production systems.
ACKNOWLEDGMENTS
We would like to acknowledge Mark Freeman, John Green, Briana
Shuford, Emily May, Dan Kane, and Nikhil Jaikumar for their assis-
tance in the field and laboratory. Cathy McMinn kindly performed
inorganic N analyses on lysimeter water. This work was funded by a
USDA Organic Research and Education Initiative (OREI) grant and
by the NSF Long-Term Ecological Research Program at the Kellogg
Biological Station.
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... Replacing annual crops with perennials has the potential to help reduce NO − 3 leaching to groundwater and provide other ecosystem services (Asbjornsen et al., 2014;Ferchaud and Mary, 2016). Cropping systems that include perennial grasses for conservation, forage, and biofuel production have lower NO − 3 leaching losses than corn-soybean systems, largely because perennial grasses have greater root biomass that extends deeper into the soil, increasing N recovery and reducing leaching (Culman et al., 2013b;Pugesgaard et al., 2015;Ferchaud and Mary, 2016). Deep roots may be particularly important in reducing NO − 3 leaching since they can expand the total volume of soil from which NO − 3 -N is taken up, and because NO − 3 is highly mobile and more prone to leaching from deep soil horizons (Maeght et al., 2013). ...
... Although total growing season ET and drainage were similar between IWG and corn, soil water content was lower under IWG compared to corn and switchgrass at 50 and 100 cm depths (Jungers et al., 2019), suggesting that soil moisture may be stored in other regions of the soil profile. Compared to annual wheat (Triticum aestivum L.), IWG had lower soil moisture up to a depth of 70-100 cm, which was associated with NO − 3 -N leaching reductions of up to 86% (Culman et al., 2013b). The distribution of IWG root biomass and its effects on soil water content throughout the soil profile are largely unknown. ...
... Michigan during stand establishment (Culman et al., 2013b). Despite the slightly higher soil solution NO − 3 -N concentrations observed in Year 1 here and on other sandy soils, values were comparable to mixtures of perennial grasses and forbs found in CRP plantings (Randall et al., 1997) and consistently below the EPA safe drinking standard of 10 mg L −1 . ...
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Nitrate (NO3--N) leaching into groundwater as a result of high nitrogen (N) fertilizer rates to annual crops presents human health risks and high costs associated with water treatment. Leaching is a particularly serious concern on sandy soils overlying porous bedrock. Intermediate wheatgrass (IWG) [Thinopyrum intermedium (Host.) Barkw. & D.R. Dewey], is a perennial grass that is being bred to produce agronomically and economically viable grain, which is commercially available as Kernza®. Intermediate wheatgrass is a low-input crop has the potential to produce profitable grain and biomass yields while reducing NO3--N leaching on sandy soils compared with common annual row crop rotations in the Upper Midwest. We compared grain yields, biomass yields, soil solution NO3--N concentration, soil extractable NO3--N, soil water content, and root biomass under IWG and a conventionally managed corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotation for 3 years on a Verndale sandy loam in Central Minnesota. Mean soil solution NO3--N was 77–96% lower under IWG than the annual crop rotation. Soil water content was greater under annuals compared to IWG early in the growing season, suggesting greater water use by IWG during this time. Interactions between crop treatments and depth were observed for soil water content in Year 3. Root biomass from 0 to 60 cm below the soil surface was five times greater beneath IWG compared to soybean, which may explain differences in soil extractable and solution NO3--N among crops. With irrigation on coarse structured soils, IWG grain yields were 854, 434, and 222 kg ha−1 for Years 1–3 and vegetative biomass averaged 4.65 Mg ha−1 yr−1; comparable to other reports on heavier soils in the region. Annual crop grain yields were consistent with local averages. These results confirm that IWG effectively reduces soil solution NO3--N concentrations even on sandy soils, supporting its potential for broader adoption on land vulnerable to NO3--N leaching.
... One of the main reasons why IWG has received much attention for its development and use is the environmental benefits it provides, attributed to its extensive root system. This root system effectively sequesters carbon, thus helping to improve soil health while reducing greenhouse gas emissions (Culman et al., 2013;Glover et al., 2010). IWG was shown to have 15 times more root growth and almost double the amount of aboveground biomass than annual wheat (Sprunger et al., 2018), leading to a 13% increase in carbon sequestration and 86% less nitrate leaching when compared to wheat (Culman et al., 2013). ...
... This root system effectively sequesters carbon, thus helping to improve soil health while reducing greenhouse gas emissions (Culman et al., 2013;Glover et al., 2010). IWG was shown to have 15 times more root growth and almost double the amount of aboveground biomass than annual wheat (Sprunger et al., 2018), leading to a 13% increase in carbon sequestration and 86% less nitrate leaching when compared to wheat (Culman et al., 2013). Moreover, nitrate leaching from the IWG was found to be one to two orders of magnitude lower than that of annual maize (Jungers et al., 2019). ...
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In this study, the effects of extrusion conditions such as feed moisture content (20%, 24%, and 28%), screw speed (200, 300, and 400 rpm), and extrusion temperature (130, 150, and 170°C) on the physical and functional properties (moisture content, expansion ratio, bulk density, hardness, water absorption index [WAI], water solubility index [WSI]) of intermediate wheatgrass (IWG) were investigated for the first time. Response surface methodology was used to model and optimize the extrusion conditions to produce expanded IWG. The model coefficient of determination (R2) was high for all the responses (0.87–0.98). All the models were found to be significant (p < 0.05) and were validated with independent experiments. Generally, all the extrusion conditions were found to have significant effects on the IWG properties measured. Increasing the screw speed and decreasing the extrusion temperature resulted in IWG extrudates with a high expansion ratio. This also resulted in IWG extrudates with generally low hardness and bulk density. Screw speed was found to have the most significant effect on the WAI and WSI, with increasing screw speed resulting in a significant (p < 0.05) decrease in WAI and a significant (p < 0.05) increase in WSI. The optimum conditions for obtaining an IWG extrudate with a high expansion ratio and WAI were found to be 20% feed moisture, 200 –356 rpm screw speed, and 130–154°C extrusion temperature. Extrusion cooking was employed in the production of expanded IWG. This research could provide a foundation to produce expanded IWG, which can potentially be used as breakfast cereals and snacks. This is critical in the efforts to commercialize IWG for mainstream food applications.
... As a result of many years of work at the Land Institute, the wheatgrass variety Kernza was developed (named after the residents of Kansas), used both for seed production, green mass, and hay (haylage). During the second year of the cultivating of the variety, there was an 86 % nitrate re-The use of wheatgrass (Thinopyrum intermedium) in breeding duction in groundwater, and a 13 % increase in soil carbon sequestration compared to annual crops (Glover et al., 2010;Culman et al., 2013;DeHaan, Van Tassel, 2014;Pugliese et al., 2019). Kernza is practically not affected by diseases and pests, the crop requires fewer agrotechnical operations, such as nitrogen fertilizers, tillage, presowing seed treatment, and fungicide protection, thereby reducing energy and economic costs (DeHaan et al., 2005;Pugliese et al., 2019). ...
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Wheatgrass ( Th. intermedium ) has been traditionally used in wheat breeding for obtaining wheat-wheatgrass hybrids and varieties with introgressions of new genes for economically valuable traits. However, in the 1980s in the United States wheatgrass was selected from among perennial plant species as having promise for domestication and the development of dual-purpose varieties for grain (as an alternative to perennial wheat) and hay. The result of this work was the creation of the wheatgrass varieties Kernza (The Land Institute, Kansas) and MN-Clearwater (University of Minnesota, Minnesota). In Omsk State Agrarian University, the variety Sova was developed by mass selection of the most winter-hardy biotypes with their subsequent combination from the population of wheatgrass obtained from The Land Institute. The average grain yield of the variety Sova is 9.2 dt/ha, green mass is 210.0 dt/ ha, and hay is 71.0 dt/ha. Wheatgrass is a crop with a large production potential, beneficial environmental properties, and valuable grain for functional food. Many publications show the advantages of growing the Kernza variety compared to annual crops in reducing groundwater nitrate contamination, increasing soil carbon sequestration, and reducing energy and economic costs. However, breeding programs for domestication of perennial crops are very limited in Russia. This paper presents an overview of main tasks faced by breeders, aimed at enhancing the yield and cultivating wheatgrass efficiency as a perennial grain and fodder crop. To address them, both traditional and modern biotechnological and molecular cytogenetic approaches are used. The most important task is to transfer target genes of Th. intermedium to modern wheat varieties and decrease the level of chromatin carrying undesirable genes of the wild relative. The first consensus map of wheatgrass containing 10,029 markers was obtained, which is important for searching for genes and their introgressions to the wheat genome. The results of research on the nutritional and technological properties of wheatgrass grain for the development of food products as well as the differences in the quality of wheatgrass grain and wheat grain are presented.
... Currently, the crop is produced at a small scale in the USA, sold under the trade name Kernza R , and incorporated into specialty products (DeHaan and Ismail, 2017). The yield potential of intermediate wheatgrass is currently half that of wheat grown under similar conditions (Culman et al., 2013), making the development of high yielding genotypes a key priority. Therefore, breeding programs have been initiated with the aim of increasing both agronomic performance and grain yield (DeHaan et al., 2005(DeHaan et al., , 2020, for which progress is being greatly accelerated through the application of genomic selection at the seedling stage (Crain et al., 2021a,b). ...
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Perennial grain crops could make a valuable addition to sustainable agriculture, potentially even as an alternative to their annual counterparts. The ability of perennials to grow year after year significantly reduces the number of agricultural inputs required, in terms of both planting and weed control, while reduced tillage improves soil health and on-farm biodiversity. Presently, perennial grain crops are not grown at large scale, mainly due to their early stages of domestication and current low yields. Narrowing the yield gap between perennial and annual grain crops will depend on characterizing differences in their life cycles, resource allocation, and reproductive strategies and understanding the trade-offs between annualism, perennialism, and yield. The genetic and biochemical pathways controlling plant growth, physiology, and senescence should be analyzed in perennial crop plants. This information could then be used to facilitate tailored genetic improvement of selected perennial grain crops to improve agronomic traits and enhance yield, while maintaining the benefits associated with perennialism.
... IWG production was found to improve physical and chemical aspects of soil health including sorptivity and mean weight diameter of wet aggregates (Rakkar et al. in review) and soil permanganate oxidizable carbon (C) (Sprunger et al., 2019). Improvements in water quality were also observed beneath IWG compared to annuals in the form of reduced nitrate leaching to groundwater (Culman et al., 2013;Jungers et al., 2019). Intermediate wheatgrass has been shown to have higher net C uptake and greater C allocation to belowground biomass than annuals, which suggests potential for soil C sequestration and atmospheric CO 2 offsets (de Oliveira et al., 2018;Bergquist, 2019). ...
Article
Perennial grain crops are being developed to reduce the negative environmental impacts of tillage and chemical inputs related to annual row-crop agriculture. To further improve the ecological benefits of perennial grains like Kernza® intermediate wheatgrass (IWG) [Thinopyrum intermedium (Host.) Barkw. & D.R. Dewey], intercropping with perennial legumes has the potential to diversify grain production systems and reduce mineral N fertilizer requirements; however, the facilitative vs. competitive effects of various legume species on perennial grain yields are unknown. We compared grain and biomass yields, tissue C:N ratio, and δ¹⁵N of IWG in response to either mineral fertilizer treatments or intercropping with one of six legume species at three locations for three years. IWG tissue C:N ratio increased through time at all sites suggesting a consistent increase in N limitation. Although no legume intercrop consistently affected grain yields through time or across sites, very rarely did an intercrop reduce grain yields to levels less than fertilized and unfertilized IWG monocultures. However, legume biomass in year 1 was negatively correlated with IWG grain yields in year 1, suggesting that negative effects of competition may outweigh positive effects of N fixation and transfer the year following establishment. The relationship between legume biomass and IWG grain yield became positive by year 3, indicating a potential lag in the positive effects of legume intercrop on grain yield. At one location, red clover (Trifolium repens L.) biomass was higher than all other legume treatments in year 1 and declined through time, giving way to a subsequent increase in IWG biomass and grain yields through time. At this site, N transfer from legumes to IWG determined by δ¹⁵N was positive by year 3 for red clover and two other legume species. This study provides evidence that legume intercrops can benefit IWG production under certain conditions, but outcomes are site-specific and may depend on conditions related to soil N levels, temperature and precipitation patterns, and weed pressure. Research is needed to identify specific traits that promote legume coexistence and facilitation with IWG, and how these traits might rank in importance depending on environmental conditions.
... Currently, the crop is produced at a small scale in the USA, sold under the trade name Kernza R , and incorporated into specialty products (DeHaan and Ismail, 2017). The yield potential of intermediate wheatgrass is currently half that of wheat grown under similar conditions (Culman et al., 2013), making the development of high yielding genotypes a key priority. Therefore, breeding programs have been initiated with the aim of increasing both agronomic performance and grain yield (DeHaan et al., 2005(DeHaan et al., , 2020, for which progress is being greatly accelerated through the application of genomic selection at the seedling stage (Crain et al., 2021a,b). ...
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Full-text available
Perennial grain crops could make a valuable addition to sustainable agriculture, potentially even as an alternative to their annual counterparts. The ability of perennials to grow year after year significantly reduces the number of agricultural inputs required, in terms of both planting and weed control, whilst reduced tillage improves soil health and on-farm biodiversity. Presently, perennial grain crops are not grown at large scale, mainly due to their early stages of domestication and current low yields. Narrowing the yield gap between perennial and annual grain crops will depend on characterizing differences in their life cycles, resource allocation, and reproductive strategies and understanding the trade-offs between annualism, perennialism, and yield. The genetic and biochemical pathways controlling plant growth, physiology, and senescence should be analyzed in perennial crop plants. This information could then be used to facilitate tailored genetic improvement in selected perennial grain crops to improve agronomic traits and enhance yield, whilst maintaining the benefits associated with perennialism.
... Moreover, it reduces the extent of soil erosion, and the precious upper surface of the soil is conserved for sustainable plant growth and yield production. Thus, the development of perennial legumes with novel nutritional properties, and eco-physiological attributes can be a valuable addition to legume production in modern and sustainable agricultural production (Culman et al., 2013). ...
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Legumes are key to food security-enhancing the sustainability of agricultural systems by virtue of their ability to engage in beneficial root-microbe symbioses and producing protein-dense edible tissues. Despite their nutritional value, legume production around the globe is challenged by various abiotic, biotic, and edaphic factors. Although classical breeding strategies have been extensively deployed in the Fabaceae family for crop improvement, the rates of favorable genetic gain in legumes trail behind the rapid progress attained in the breeding of staple cereals. However, the gradual development of legume genomic resources and breeding technologies over the past 15 years have begun to provide application benefits and, presently, have generated a revolution in targeted legume breeding projects facilitated by comparative genomics. These advances include the assembly of legume genetic maps and determination of linkage markers, genomic and transcriptomic sequencing, gene assembly and annotation, the development of association mapping methods, synteny and structural variant analyses, protocols for functional explorations in vivo, and advancement in trait mapping. In this chapter, we discuss the innovative progress in legume breeding resources in a postgenomics context and present their application toward securing sustainable food production within an agricultural system that is challenged by climate change and nutrient scarcity. Moreover, the role of different genetic enhancement programs in facilitating legume breeding strategies has also been discussed.
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In semiarid regions of the western United States, there is heightened interest in tree removal to increase water availability for other uses such as forage growth and groundwater recharge. This study was conducted in central New Mexico to determine the effects of heavy infrequent defoliation of chemically thinned juniper woodland (Juniperus monosperma) on soil moisture. Each of three cattle-grazing exclosures (CD, FG, and KI) was instrumented: 1) beneath trees with a set of three soil moisture probes (0−25, 25−50, and 50−75 cm depth) and one soil temperature probe under live trees (control) and dead trees (herbicide-treated); and 2) between trees with one soil moisture and one soil temperature probe in control and herbicide-treated intercanopy plots. Each plot had three clipped and three unclipped subplots. Mean daily maximum surface soil temperature was highest (17.19°C) in intercanopy, intermediate (16.13°C) under herbicide-treated, and lowest (14.90°C) under control trees. Topsoil moisture (0−25 cm depth) was different among treatment combinations from late July to early September 2006. Thus, the control unclipped combination had the highest topsoil moisture while the herbicide-treated unclipped combination had the lowest topsoil moisture. Comparing other depths, control unclipped plots had higher soil moisture in the middle layer (25−50 cm) and bottom layer (50−75 cm) than at the top from late August to early November 2006. Results imply that clipping on chemically thinned juniper woodlands does not increase soil moisture at any depth, yet macropore flow and water absorption on deep soil layers, underneath live trees, might help to store soil moisture for longer periods in water-limited environments.
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Reproductive growth and development of cool‐season grasses is primarily driven by air temperature and photoperiod. This study was conducted near Salina, KS, to model the effects of growing degree days (GDD), day of the year (DOY), and cropping systems on first‐ and second‐year intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] (IWG) in Kernza perennial grain production systems. In 2018 and 2019, GDD and DOY were highly correlated with reproductive growth and development (i.e., mean stage count, head meristem height, and leaf, stem, and head biomass fractions). Row spacing, fertilization, and intercropping with alfalfa (Medicago sativa L.) did not influence IWG reproductive growth and development. Across years, DOY more closely predicted reproductive stages than GDD, indicating a greater response to photoperiod than air temperature. After stem initiation, the fraction of total biomass allocated to leaves decreased, whereas stem and head biomass increased in response to GDD and DOY. At anthesis, stem biomass exceeded leaf and head biomass. Parameterizing GDD and DOY models for management in IWG dual‐purpose, Kernza grain production systems will require additional datasets from many locations and environments. Day of the year and growing degree days can be used to estimate intermediate wheatgrass reproductive development. Intermediate wheatgrass reproductive growth and development respond similarly in monoculture and bicultures. Intermediate wheatgrass biomass fractions were similar across years.
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No-till management has been shown to increase soil aggregation, reduce erosion rates, and increase soil organic matter across a range of soil types, cropping systems, and climates. Few agricultural practices provide similar opportunities to deliver positive benefits for farmers, society, and the environment. The potential benefits of no-till are not being fully realized, however, in large part because no-till is rarely practiced continuously and many fields suitable for no-till are still conventionally tilled. We present here three arguments, based on recent research, in support of the agronomic and environmental benefits of continuous no-till: (i) although there exist agronomic challenges with no-till, long-term yields in these systems can equal or exceed those in tilled soils; (ii) cultivating no-till systems can decrease soil aggregation and accelerate C and N losses so rapidly that years of soil restoration can be undone within weeks to months; and (iii) over time, changes in soil structure and organic matter, coupled with producer adaptation to the need for spatially and temporally explicit chemical applications, increase plant N availability and reduce environmental N losses. At least in theory, then, continuous no-till can be widely practiced to improve the environment and maintain yields with little or no economic sacrifice by producers. In practice, however, many diverse challenges still limit no-till adoption in different regions. These challenges are surmountable, but potential solutions need to be interdisciplinary and address the ecological and especially the social and economic constraints to deploying continuous no-till.
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